lstopo: warn when ignoring output file because we don't know the output type
lstopo: warn when ignoring output file because we don't know the output type

If the output has no extension and --of isn't used, we don't what to output,
and therefore we ignore the output file entirely.
Now warn about this.



git-svn-id: 14be032f8f42541b1a281b51ae8ea69814daf20e@5079 4b44e086-7f34-40ce-a3bd-00e031736276

BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc